1. Field of the Invention
The present invention relates to a measurement device, such as a total station or an electronic tacheometer, and, more particularly, to a measurement device provided with a function in which an instrument height is sensed.
2. Description of the Related Art
Due to recent advances in electronics technology, a device has been developed, enabling an electronic distance measurements to be performed, in which a light wave, radiated along an optical axis, is reflected by an object and received, thereby allowing a distance between the device and the object to be derived. The electronic distance measurement is carried out in such a manner that a known point in the measurement device is set as the origin, and the origin is fixed with respect to a vertical line passing through a station on the ground. For calculating the altitude of the station from the distance measurement data obtained by the measurement device, a vertical distance between the origin and the station, i.e. the instrument height, is required.
Conventionally, a measurement of the instrument height has been carried out in such a manner that an end of a tape measure is attached to an engaging metal fitting, disposed on a side surface of the main body of the measurement device, so that the other end of the tape measure extends to the ground, enabling the scale formed on the tape measure to be read.
However, by engaging the tape measure with a side surface of the main body of the measurement device, since a position where the tape measure is attached and the station of the ground are horizontally spaced apart from each other, an error easily occurs in the resulting measurement of the instrument height. Further, since the accuracy of the tape measure is low, it is difficult to detect the instrument height with a high degree of accuracy, and therefore, the accuracy of the resulting measurement would be low even if a highly accurate distance measurement was carried out using an electronic distance meter.